Analysis of Polycyclic Aromatic Hydrocarbons on Vapor-Grown Carbon Fibers

Abstract

The ability to grow carbon fibers by pyrolysis of gas phase hydrocarbons in the presence of catalytic iron particles holds the promise of new technologies for low-cost production of novel fibers with improved mechanical properties for use in existing or new manufacturing applications. As part of a research effort to investigate methods for producing vapor-grown carbon fibers, a series of fiber samples were analyzed for their content of polycyclic aromatic hydrocarbons (PAH) which are an undesirable by-product of many industrial pyrolysis processes. Adsorbed hydrocarbons were extracted and analyzed by both capillary gas chromatography (GC/FID & GC/MS) and the Ames bacterial mutation assay. PAH compounds were readily detected in most carbon fiber extracts. The highest concentrations (1% – 5% sample mass) were detected on fibers produced by a continuous flow-through reactor. Much lower concentrations (<0.2%) were found on fibers produced by batch processes. Most prominent PAH components, containing 2–6 aromatic rings, were identified with available reference compounds. Use of an aluminum-clad column also permitted analysis of high-molecular-weight-PAH (C26–C34) which contributed from 1% to 80% of the total PAH in various samples. Distinctly different patterns of PAH isomer distribution were found in these samples which can be correlated with changes in the proportionate contributions of individual PAH compounds to the mutagenic activity of the total extract. The extent of exposure to PAH from handling fibers and the likely significance of an association between genotoxic chemicals and potentially respirable fibers require further consideration, but these results have demonstrated the importance of continuing efforts to minimize production of PAH and their retention on vapor-grown carbon fibers.